Gregg Alton, executive vice president for Gilead's corporate and medical affairs, said that Sovaldi, which costs $84 000 for a 12-week course of treatment, is a cheaper option than older therapies, which cost as much as $200 000.

Alton acknowledged that some insurers, such as Express Scripts, have expressed concerns about the therapy's price, while UnitedHealth Group noted that the drug reduced its first-quarter profits.